The majority of large locomotives in use today are powered by turbocharged diesel engines. While such engines are quite powerful yet relatively economical to operate, the life of the turbocharger used on these locomotives has proved to be quite short, about two years or less. As these turbochargers are quite expensive to replace or repair, this limitation has presented a substantial problem to the industry, a problem which has heretofore been unsolved.
The short life of the turbochargers used on these engines has been found to result frequently from overspeeding which occurs as a result of fires in the air box and exhaust manifold. The air box is the housing which extends the length and width of the diesel engine, about the crank case and a portion of the liner disposed about the engine pistons. When a fire occurs in the air box, not only can the engine be damaged, but the temperature of the exhaust gases which runs the turbocharger increases causing the rotational speed of the turbocharger to increase and overspeed. When the turbocharger overspeeds, the blades grow into the surrounding shrouds and tear, resulting in severe damage or even a total loss of the turbocharger. Fires in the exhaust manifold have the same resulting effects.
Air box fires are common and generally result from the belching of fire from the engine cylinders back through the air intake ports into the air box which ignites the oil which has accumulated therein. This oil build-up within the air box results from the cooling oil which is squirted onto the pistons and accumulates when the side vents become plugged which are designed to channel away the cooling oil into a protected oil sump. In addition, when the pistons are moving downward and the air intake ports open, combustion is still ocurring within the cylinders and the pressure within the cylinders is not totally dissipated by expansion, a snuff back results wherein the oil is blown through the ports, coating the air box around the liner. This results in highly inflammable air box interior which is easily ignited when burning fuel is also belched back through the ports into the air box. Exhaust manifold fires are usually caused by an accumulation of lube oil and fuel resulting from malfunctioning or defective valve guides or rings. As the engineer is not positioned near the air box or exhaust manifold while the engine is running, these fires are not quickly detected and the turbocharger overspeed occurs quite rapidly. Hence, the very short life of these turbochargers. In fact, even when the fires were rapidly detected, the industry has not heretofore found any means of preventing the onsuing overspeed due to its inability of finding a way immediately to shut down the locomotive engine. When the throttle is quickly closed, cutting off the normal fuel flow, these diesel engines will burn the fuel partially consumed by the fire and continue to run for a period of time sufficiently long to cause the turbocharger overspeed. As a result, the industry has continued to endure the high costs of turbocharger repair and replacement.
Another related problem is the occurrence of a fire in the electrical cabinet on the locomotive. As such fires similarly go unnoticed for a period of time, the engine continues to drive the generator which feeds the fire which can result in the destruction or severe damage of not only the electrical equipment but the engine as well. If the engine could be shutdown immediately upon the occurrence of such a fire, the generator would stop and such fires could be readily extinguished before they could cause such damage.
It would therefore be highly desirable to provide a means by which the diesel engine and turbocharger in a locomotive could be immediately shutdown upon the occurrence of a fire in either the engine or electrical equipment whereby the life of such parts as engine components, turbocharger and electrical equipment could be greatly extended. The shutdown mechanism disclosed and claimed herein has been found to be highly successful in accomplishing this purpose.